Lumasiran, an RNAi Therapeutic for Primary Hyperoxaluria Type 1.

BACKGROUND: Primary hyperoxaluria type 1 (PH1) is a rare genetic disease caused by hepatic overproduction of oxalate that leads to kidney stones, nephrocalcinosis, kidney failure, and systemic oxalosis. Lumasiran, an investigational RNA interference (RNAi) therapeutic agent, reduces hepatic oxalate production by targeting glycolate oxidase. METHODS: In this double-blind, phase 3 trial, we randomly assigned (in a 2:1 ratio) patients with PH1 who were 6 years of age or older to receive subcutaneous lumasiran or placebo for 6 months (with doses given at baseline and at months 1, 2, 3, and 6). The primary end point was the percent change in 24-hour urinary oxalate excretion from baseline to month 6 (mean percent change across months 3 through 6). Secondary end points included the percent change in the plasma oxalate level from baseline to month 6 (mean percent change across months 3 through 6) and the percentage of patients with 24-hour urinary oxalate excretion no higher than 1.5 times the upper limit of the normal range at month 6. RESULTS: A total of 39 patients underwent randomization; 26 were assigned to the lumasiran group and 13 to the placebo group. The least-squares mean difference in the change in 24-hour urinary oxalate excretion (lumasiran minus placebo) was -53.5 percentage points (P<0.001), with a reduction in the lumasiran group of 65.4% and an effect seen as early as month 1. The between-group differences for all hierarchically tested secondary end points were significant. The difference in the percent change in the plasma oxalate level (lumasiran minus placebo) was -39.5 percentage points (P<0.001). In the lumasiran group, 84% of patients had 24-hour urinary oxalate excretion no higher than 1.5 times the upper limit of the normal range at month 6, as compared with 0% in the placebo group (P<0.001). Mild, transient injection-site reactions were reported in 38% of lumasiran-treated patients. CONCLUSIONS: Lumasiran reduced urinary oxalate excretion, the cause of progressive kidney failure in PH1. The majority of patients who received lumasiran had normal or near-normal levels after 6 months of treatment. (Funded by Alnylam Pharmaceuticals; ILLUMINATE-A ClinicalTrials.gov number, NCT03681184.).

Acute glomerulonephritis with concurrent suspected bacterial pneumonia - is it the tip of the iceberg?

BACKGROUND: Post infectious glomerulonephritis is the most common glomerulopathy in children, occurring several weeks after nephritogenic streptococcal throat or skin infection. Reports of acute glomerulonephritis (AGN) occurring during active bacterial pneumonia in children are rare. The aim of this study was to evaluate the incidence of AGN concurrent with bacterial pneumonia in children. METHODS: We reviewed records of all children admitted with a diagnosis of pneumonia to the pediatric department in a single tertiary medical center between January 2015 and April 2023. Patients with bacterial pneumonia and concurrent glomerulonephritis were included. RESULTS: Eleven (0.98%) of 1,123 patients with bacterial pneumonia had concurrent AGN. All were males with a median age of 2.7 years (range 1-13). Mean time from bacterial pneumonia onset to acute glomerulonephritis symptoms was 2.7 ± 1.5 days. Five (45%) patients had evidence of pneumococcal infection. Hypertension was found in 10 (91%) patients. Mean trough eGFR was 43.5 ± 21.4 ml/min/1.73 m2 (range 11-73). Ten patients (91%) had low C3 levels. Median urinary protein-to-creatinine ratio was 2.5 mg/mg (IQR 2.15-14.75). All patients fully recovered. Microscopic hematuria was the last finding to normalize after a median of 29.5 days (IQR 17.25-38). CONCLUSION: AGN during bacterial pneumonia may be more frequent than previously recognized. Kidney prognosis was excellent in all patients. Prospective studies are needed to evaluate the impact of this condition.

Diagnosis and management of primary hyperoxalurias: best practices.

The primary hyperoxalurias (PH 1, 2, and 3) are rare autosomal recessive disorders of glyoxylate metabolism resulting in hepatic overproduction of oxalate. Clinical presentations that should prompt consideration of PH include kidney stones, nephrocalcinosis, and kidney failure of unknown etiology, especially with echogenic kidneys on ultrasound. PH1 is the most common and severe of the primary hyperoxalurias with a high incidence of kidney failure as early as infancy. Until the recent availability of a novel RNA interference (RNAi) agent, PH care was largely supportive of eventual need for kidney/liver transplantation in PH1 and PH2. Together with the Oxalosis and Hyperoxaluria Foundation, the authors developed a diagnostic algorithm for PH1 and in this report outline best clinical practices related to its early diagnosis, supportive treatment, and long-term management, including the use of the novel RNAi. PH1-focused approaches to dialysis and kidney/liver transplantation for PH patients with progression to chronic kidney disease/kidney failure and systemic oxalosis are suggested. Therapeutic advances for this devastating disease heighten the importance of early diagnosis and informed treatment.

Lumasiran for Advanced Primary Hyperoxaluria Type 1: Phase 3 ILLUMINATE-C Trial.

RATIONALE & OBJECTIVE: Lumasiran reduces urinary and plasma oxalate (POx) in patients with primary hyperoxaluria type 1 (PH1) and relatively preserved kidney function. ILLUMINATE-C evaluates the efficacy, safety, pharmacokinetics, and pharmacodynamics of lumasiran in patients with PH1 and advanced kidney disease. STUDY DESIGN: Phase 3, open-label, single-arm trial. SETTING & PARTICIPANTS: Multinational study; enrolled patients with PH1 of all ages, estimated glomerular filtration rate ≤45 mL/min/1.73 m2 (if age ≥12 months) or increased serum creatinine level (if age <12 months), and POx ≥20 µmol/L at screening, including patients with or without systemic oxalosis. INTERVENTION: Lumasiran administered subcutaneously; 3 monthly doses followed by monthly or quarterly weight-based dosing. OUTCOME: Primary end point: percent change in POx from baseline to month 6 (cohort A; not receiving hemodialysis at enrollment) and percent change in predialysis POx from baseline to month 6 (cohort B; receiving hemodialysis at enrollment). Pharmacodynamic secondary end points: percent change in POx area under the curve between dialysis sessions (cohort B only); absolute change in POx; percent and absolute change in spot urinary oxalate-creatinine ratio; and 24-hour urinary oxalate adjusted for body surface area. RESULTS: All patients (N = 21; 43% female; 76% White) completed the 6-month primary analysis period. Median age at consent was 8 (range, 0-59) years. For the primary end point, least-squares mean reductions in POx were 33.3% (95% CI, -15.2% to 81.8%) in cohort A (n = 6) and 42.4% (95% CI, 34.2%-50.7%) in cohort B (n = 15). Improvements were also observed in all pharmacodynamic secondary end points. Most adverse events were mild or moderate. No patient discontinued treatment or withdrew from the study. The most commonly reported lumasiran-related adverse events were injection-site reactions, all of which were mild and transient. LIMITATIONS: Single-arm study without placebo control. CONCLUSIONS: Lumasiran resulted in substantial reductions in POx with acceptable safety in patients with PH1 who have advanced kidney disease, supporting its efficacy and safety in this patient population. FUNDING: Alnylam Pharmaceuticals. TRIAL REGISTRATION: Registered at ClinicalTrials.gov with study number NCT04152200 and at EudraCT with study number 2019-001346-17. PLAIN-LANGUAGE SUMMARY: Primary hyperoxaluria type 1 (PH1) is a rare genetic disease characterized by excessive hepatic oxalate production that frequently causes kidney failure. Lumasiran is an RNA interference therapeutic that is administered subcutaneously for the treatment of PH1. Lumasiran has been shown to reduce oxalate levels in the urine and plasma of patients with PH1 who have relatively preserved kidney function. In the ILLUMINATE-C study, the efficacy and safety of lumasiran were evaluated in patients with PH1 and advanced kidney disease, including a cohort of patients undergoing hemodialysis. During the 6-month primary analysis period, lumasiran resulted in substantial reductions in plasma oxalate with acceptable safety in patients with PH1 complicated by advanced kidney disease.

Efficacy and safety of lumasiran for infants and young children with primary hyperoxaluria type 1: 12-month analysis of the phase 3 ILLUMINATE-B trial.

BACKGROUND: Primary hyperoxaluria type 1 (PH1) is a rare genetic disease that causes progressive kidney damage and systemic oxalosis due to hepatic overproduction of oxalate. Lumasiran demonstrated efficacy and safety in the 6-month primary analysis period of the phase 3, multinational, open-label, single-arm ILLUMINATE-B study of infants and children < 6 years old with PH1 (ClinicalTrials.gov: NCT03905694 (4/1/2019); EudraCT: 2018-004,014-17 (10/12/2018)). Outcomes in the ILLUMINATE-B extension period (EP) for patients who completed ≥ 12 months on study are reported here. METHODS: Of the 18 patients enrolled in the 6-month primary analysis period, all entered the EP and completed ≥ 6 additional months of lumasiran treatment (median (range) duration of total exposure, 17.8 (12.7-20.5) months). RESULTS: Lumasiran treatment was previously reported to reduce spot urinary oxalate:creatinine ratio by 72% at month 6, which was maintained at 72% at month 12; mean month 12 reductions in prespecified weight subgroups were 89%, 68%, and 71% for patients weighing < 10 kg, 10 to < 20 kg, and ≥ 20 kg, respectively. The mean reduction from baseline in plasma oxalate level was reported to be 32% at month 6, and this improved to 47% at month 12. Additional improvements were also seen in nephrocalcinosis grade, and kidney stone event rates remained low. The most common lumasiran-related adverse events were mild, transient injection-site reactions (3 patients (17%)). CONCLUSIONS: Lumasiran treatment provided sustained reductions in urinary and plasma oxalate through month 12 across all weight subgroups, with an acceptable safety profile, in infants and young children with PH1. A higher resolution version of the Graphical abstract is available as Supplementary information.

Phase 3 trial of lumasiran for primary hyperoxaluria type 1: A new RNAi therapeutic in infants and young children.

PURPOSE: Primary hyperoxaluria type 1 (PH1) is a rare, progressive, genetic disease with limited treatment options. We report the efficacy and safety of lumasiran, an RNA interference therapeutic, in infants and young children with PH1. METHODS: This single-arm, open-label, phase 3 study evaluated lumasiran in patients aged <6 years with PH1 and an estimated glomerular filtration rate >45 mL/min/1.73 m2, if aged ≥12 months, or normal serum creatinine, if aged <12 months. The primary end point was percent change in spot urinary oxalate to creatinine ratio (UOx:Cr) from baseline to month 6. Secondary end points included proportion of patients with urinary oxalate ≤1.5× upper limit of normal and change in plasma oxalate. RESULTS: All patients (N = 18) completed the 6-month primary analysis period. Median age at consent was 50.1 months. Least-squares mean percent reduction in spot UOx:Cr was 72.0%. At month 6, 50% of patients (9/18) achieved spot UOx:Cr ≤1.5× upper limit of normal. Least-squares mean percent reduction in plasma oxalate was 31.7%. The most common treatment-related adverse events were transient, mild, injection-site reactions. CONCLUSION: Lumasiran showed rapid, sustained reduction in spot UOx:Cr and plasma oxalate and acceptable safety in patients aged <6 years with PH1, establishing RNA interference therapies as safe, effective treatment options for infants and young children.

Association of post-transplantation anellovirus viral load with kidney transplant rejection in children.

BACKGROUND: Post-transplantation immunosuppressive therapy reduces the risk of graft rejection but raises the risk of infection and malignancy. A biomarker of the level of immunosuppression can be helpful in monitoring immunosuppressive therapy. Inverse correlation between Torque teno virus (TTV) from the Anelloviridae (AV) family load and immune competence was described in previous studies. The aim of this study was to analyze the association between AV family viruses' kinetics and the risk for graft rejection in the first year after kidney transplantation in children. METHODS: The titers of three genera (TTV, TTMDV, and TTMV) from the AV family were monitored by real-time PCR in consecutive samples from children before and after kidney transplantation. RESULTS: Twenty-one children who underwent kidney transplantation were enrolled. Five out of 21 patients experienced acute graft rejection within a year from transplantation. We found that in patients who experienced graft rejection, the median titers of TTV and total AV titers at 5-6 months post-transplantation were lower than in those who did not. Using a threshold determined by ROC analysis, significant differences in TTV and total AV load were found between patients who had or did not have graft rejection (p = 0.002 and 0.004, respectively). No association was found between the dominance of any AV genus titer and the likelihood of rejection. CONCLUSION: This pilot study suggests that children after kidney transplantation with low TTV and total AV titers 5-6 months post-transplantation are at increased risk for graft rejection within a year after transplantation. A higher resolution version of the Graphical abstract is available as Supplementary information.

Metabolic alkalosis in infants treated with peritoneal dialysis.

BACKGROUND: Acid-base balance is maintained by kidney excretion of titratable acids and bicarbonate reabsorption. Metabolic alkalosis is uncommon in dialysis-treated patients. The aim of this retrospective study was to assess the rate of metabolic alkalosis in pediatric patients treated with peritoneal dialysis. METHODS: Medical records of children treated with peritoneal dialysis in Shaare Zedek Medical Center from January 2000 to June 2021 were reviewed and compared with young adults currently treated with peritoneal dialysis. Demographic, clinical, and peritoneal dialysis characteristics were extracted from the medical records. RESULTS: Thirty chronic peritoneal dialysis patients were included in our study, seven under 2 years, 13 between 2 and 18 years, and 10 adults. 90.3% of the measurements in infants showed metabolic alkalosis compared to 32.3% in the 2-18-year group and none in the adult group. Higher size-adjusted daily exchange volume, lack of urine output, and high lactate-containing dialysate were associated with metabolic alkalosis. Alkalosis was not explained by vomiting, diuretic therapy, or carbonate-containing medications. High transport membrane, low dietary protein, and malnutrition, all previously reported explanations for metabolic alkalosis, were not found in our study. CONCLUSIONS: Metabolic alkalosis is common in infants treated with peritoneal dialysis as opposed to older children and adults. High lactate-containing dialysate is a possible explanation. Higher size-adjusted daily dialysate exchange volume, which may reflect higher bicarbonate absorption, is another independent predictor of alkalosis. Acid-base status should be closely followed in infants, and using a dialysis solution with lower bicarbonate or lactate level should be considered. A higher resolution version of the graphical abstract is available as Supplementary Information.

Catabolism of Hydroxyproline in Vertebrates: Physiology, Evolution, Genetic Diseases and New siRNA Approach for Treatment.

Hydroxyproline is one of the most prevalent amino acids in animal proteins. It is not a genetically encoded amino acid, but, rather, it is produced by the post-translational modification of proline in collagen, and a few other proteins, by prolyl hydroxylase enzymes. Although this post-translational modification occurs in a limited number of proteins, its biological significance cannot be overestimated. Considering that hydroxyproline cannot be re-incorporated into pro-collagen during translation, it should be catabolized following protein degradation. A cascade of reactions leads to production of two deleterious intermediates: glyoxylate and hydrogen peroxide, which need to be immediately converted. As a result, the enzymes involved in hydroxyproline catabolism are located in specific compartments: mitochondria and peroxisomes. The particular distribution of catabolic enzymes in these compartments, in different species, depends on their dietary habits. Disturbances in hydroxyproline catabolism, due to genetic aberrations, may lead to a severe disease (primary hyperoxaluria), which often impairs kidney function. The basis of this condition is accumulation of glyoxylate and its conversion to oxalate. Since calcium oxalate is insoluble, children with this rare inherited disorder suffer from progressive kidney damage. This condition has been nearly incurable until recently, as significant advances in substrate reduction therapy using small interference RNA led to a breakthrough in primary hyperoxaluria type 1 treatment.

Mutations in HOGA1 do Not Confer a Dominant Phenotype Manifesting as Kidney Stone Disease.

PURPOSE: The etiology of calcium-oxalate kidney stone formation remains elusive. Biallelic mutations in HOGA1 are responsible for primary hyperoxaluria type 3 and result in oxalate overproduction and kidney stone disease. Our previous study showed that carriers of HOGA1 mutations have elevated urinary levels of oxalate precursors. In this study we explored the possibility that mutations in HOGA1 confer a dominant phenotype in the form of kidney stone disease or hyperoxaluria. MATERIALS AND METHODS: An observational analytic case control study was designed to determine the prevalence of pathogenic HOGA1 mutations among adults with calcium-oxalate kidney stone disease. Given the high prevalence of HOGA1 mutations among Ashkenazi Jews, this group was evaluated separately. Carrier frequency of any of the 52 reported pathogenic mutations was compared to data derived from gnomAD for the corresponding ethnic group. Sanger sequencing of HOGA1 gene was performed on DNA samples from the following groups: 60 Ashkenazi Jews and 86 nonAshkenazi calcium-oxalate stone formers, 150 subjects with low and 150 with high urinary oxalate levels. RESULTS: The carrier prevalence of pathogenic mutations among the Ashkenazi Jews was 1.7% compared to 2.8% in the corresponding control group (p=0.9 OR=0.6 95% CI 0.01-3.51). We did not detect any mutation among the nonAshkenazi study group. No correlation was detected between hyperoxaluria and HOGA1 variants. CONCLUSIONS: This study shows that mutations in HOGA1 do not confer a dominant phenotype in the form of calcium-oxalate kidney stone disease or hyperoxaluria.

Novel therapeutic approaches for the primary hyperoxalurias.

Loss-of-function mutations in three genes, involved in the metabolic pathway of glyoxylate, result in increased oxalate production and its crystallization in the form of calcium oxalate. This leads to three forms of primary hyperoxaluria-an early-onset inherited kidney disease with wide phenotypic variability ranging from isolated kidney stone events to stage 5 chronic kidney disease in infancy. This review provides a description of metabolic processes resulting in oxalate overproduction and summarizes basic therapeutic approaches. Unfortunately, current treatment of primary hyperoxaluria does not allow the prevention of loss of kidney function or to substantially diminish other symptoms in most patients. However, latest breakthroughs in biotechnology provide new promising directions for drug development. Some of them have already progressed to the level of clinical trials; others are just at the stage of proof of concept. Here we review the most advanced technologies including those that have been harnessed as possible therapeutic modalities.

First-week urine beta-2 microglobulin levels in term healthy neonates.

BACKGROUND: Beta-2 microglobulin (ß2mG) is a low-molecular-weight protein that is almost exclusively eliminated through the kidneys. It is freely filtered in the glomeruli and almost completely reabsorbed and degraded in the proximal tubules. Normal urinary ß2mG levels are very low (between 0.04 and 0.22 mg/L). No reference values are known in infants and young children. METHODS: Urinary ß2mG levels were measured in 103 healthy term neonates during the first week of life by nephelometric technology. RESULTS: The average level of urinary ß2mG was 0.65 mg/L (95% confidence interval between 0 and 10.8 mg/L). There was a minor difference between male and female neonates but it did not reach statistical significance. There was no effect of the gestational week, birth weight, or weight loss in the first week of life, on urinary ß2mG levels. CONCLUSIONS: First-week urinary ß2mG levels in healthy term infants were higher than adult levels. Incomplete maturation of kidney tubules in neonates could be a possible explanation. These can now be used in clinical practice and further studies that assess the degree of proximal tubular function in health and disease. Graphical abstract.

Long-term complications of systemic oxalosis in children-a retrospective single-center cohort study.

BACKGROUND: Systemic oxalosis is a severe complication seen in primary hyperoxaluria type I patients with kidney failure. Deposition of insoluble calcium oxalate crystals in multiple organs leads to significant morbidity and mortality. METHODS: We describe a retrospective cohort of 11 patients with systemic oxalosis treated at our dialysis unit from 1982 to 1998 (group 1) and 2007-2019 (group 2). Clinical and demographic data were collected from medical records. Imaging studies were only available for patients in group 2 (n = 5). RESULTS: Median age at dialysis initiation was 6.1 months (IQR 4-21.6), 64% were male. Dialysis modality was mostly peritoneal dialysis in group 1 and daily hemodialysis in group 2. Bone disease was the first manifestation of systemic oxalosis, starting with the appearance of sclerotic bands (mean 166 days, range 1-235), followed by pathological fractures in long bones (mean 200.4 days, range 173-235 days). Advanced disease was characterized by vertebral fractures with resulting kyphosis, worsening splenomegaly, and adynamic bone disease. Two patients developed pulmonary hypertension, 4 and 8 months prior to their death. Four of 11 patients developed hypothyroidism 0-60 months after dialysis initiation. Only one patient survived after a successful liver-kidney transplantation. Four patients died after liver or liver-kidney transplantation. CONCLUSIONS: This is the first comprehensive description of the natural history of pediatric systemic oxalosis. We hope that our findings will provide basis for a quantitative severity score in future, larger studies.

Eosinophilia in a peritoneal dialysis patient: Answers.

Icodextrin is a starch-derived glucose polymer used in peritoneal dialysis dialysate to treat volume overload by increasing ultrafiltration in patients with end-stage renal disease. Reported adverse reactions to icodextrin are mild and rare and mainly consist of skin rash that resolves spontaneously after discontinuation of treatment. We describe a young patient with extreme eosinophilia that appeared with the use of icodextrin, disappeared after its discontinuation, and reappeared after a rechallenge with the drug. The eosinophilia was not associated with peritonitis, was asymptomatic, and fully resolved after discontinuation of the drug. Severe eosinophilia can potentially cause tissue damage in several organs, which would indicate that blood eosinophil count is recommended in routine complete blood counts while icodextrin peritoneal dialysis is being administered.

Metabolite diagnosis of primary hyperoxaluria type 3.

BACKGROUND: Primary hyperoxaluria type 3 (PH3) is a recently described cause of childhood renal calculi. It results from mutations in the HOGA1 gene and most cases have been diagnosed after clinical ascertainment, exclusion of other genetic hyperoxalurias and mutation testing. Metabolite testing has not been widely applied but holds promise for the rapid screening and diagnosis of patients who are not specifically suspected to have PH3. CASE-DIAGNOSIS/TREATMENT: Two cases presented with renal calculi. Urine metabolite testing by tandem mass spectrometry was performed as part of the routine diagnostic work-up for this condition. Both had significantly increased levels of the PH3 urine marker 4-hydroxyglutamate and related metabolites. The diagnosis of PH3 was confirmed by the finding of bi-allelic damaging HOGA1 mutations. CONCLUSIONS: Urine screening by tandem mass spectrometry is a rapid, high-throughput test that can detect PH3 cases that may otherwise not be diagnosed.

Deficiency of the sphingosine-1-phosphate lyase SGPL1 is associated with congenital nephrotic syndrome and congenital adrenal calcifications.

We identified two unrelated consanguineous families with three children affected by the rare association of congenital nephrotic syndrome (CNS) diagnosed in the first days of life, of hypogonadism, and of prenatally detected adrenal calcifications, associated with congenital adrenal insufficiency in one case. Using exome sequencing and targeted Sanger sequencing, two homozygous truncating mutations, c.1513C>T (p.Arg505*) and c.934delC (p.Leu312Phefs*30), were identified in SGPL1-encoding sphingosine-1-phosphate (S1P) lyase 1. SGPL1 catalyzes the irreversible degradation of endogenous and dietary S1P, the final step of sphingolipid catabolism, and of other phosphorylated long-chain bases. S1P is an intracellular and extracellular signaling molecule involved in angiogenesis, vascular maturation, and immunity. The levels of SGPL1 substrates, S1P, and sphingosine were markedly increased in the patients' blood and fibroblasts, as determined by liquid chromatography-tandem mass spectrometry. Vascular alterations were present in a patient's renal biopsy, in line with changes seen in Sgpl1 knockout mice that are compatible with a developmental defect in vascular maturation. In conclusion, loss of SGPL1 function is associated with CNS, adrenal calcifications, and hypogonadism.

Primary hyperoxalurias: diagnosis and treatment.

Primary hyperoxalurias (PH) comprise a group of three distinct metabolic diseases caused by derangement of glyoxylate metabolism in the liver. Recent years have seen advances in several aspects of PH research. This paper reviews current knowledge of the genetic and biochemical basis of PH, the specific epidemiology and clinical presentation of each type, and therapeutic approaches in different disease stages. Potential future specific therapies are discussed.

Severe neutropenia in children after renal transplantation: incidence, course, and treatment with granulocyte colony-stimulating factor.

BACKGROUND: Infections are an important cause of morbidity and mortality in solid organ transplant recipients. Neutrophils play a crucial role in the initial host defense against bacterial pathogens. Neutropenia is not uncommon after renal transplantation in adults; however, there are scarce published data in children. We conducted a historical cohort study to evaluate the incidence, clinical course, and management of severe neutropenia after renal transplantation in children. METHODS: In a single-center study, we collected clinical and laboratory data on all children (<20 years) who underwent renal transplantation from January 2005 to March 2014. All post-transplantation blood counts were reviewed; the lowest absolute neutrophil count was recorded and correlated with clinical information and other laboratory findings. RESULTS: Of the 72 patients studied, 46 (64%) had at least one episode of neutropenia [absolute neutrophil count (ANC) <1500/µl] during the study period, 16 of whom (22%) had severe neutropenia (ANC < 500/µl), 2-11 months (median, 3.5) after renal transplantation. Work-up for viral infection or malignancy was performed. Initial management included dose decrease and subsequent discontinuation of antimetabolite, stopping co-trimoxazole and valganciclovir. Bone marrow aspiration in four children revealed normal marrow cellularity in all cases, with myelocyte maturational arrest in two. Eight children (11%) were treated with granulocyte colony-stimulating factor (G-CSF) (5 mcg/kg/day) 1-4 doses (median, 2), with excellent response in all and no adverse effects. Eight children presented with fever during severe neutropenia, and were treated with empiric antibiotics. Mycophenolate/azathioprine were resumed in all patients unless contraindicated (pre-existing BK viremia -1, PTLD -1). Recurrence of neutropenia was seen in five patients, only one of whom required further treatment with G-CSF. Graft function was preserved during and after resolution of neutropenia. Post-transplant neutropenia in children is common, and mostly occurs in the first few months. Its etiology is probably primarily a result of the combination of immunosuppressive agents and prophylactic treatment of infections in the early post-transplant period. CONCLUSIONS: Decreasing immunosuppressive or antimicrobial medications carries the risk of acute rejection or infection. Off-label treatment with G-CSF may present a safe and effective alternative.

Maternal and infantile hypercalcemia caused by vitamin-D-hydroxylase mutations and vitamin D intake.

BACKGROUND: Hypercalcemia is caused by many different conditions and may lead to severe complications. Loss-of-function mutations of CYP24A1, encoding vitamin D-24-hydroxylase, have recently been identified in idiopathic infantile hypercalcemia and in adult kidney stone disease. The aim of this study was to investigate the genetics and clinical features of both infantile and maternal hypercalcemia. METHODS: We studied members of four unrelated Israeli families with hypercalcemia, namely, one woman during pregnancy and after delivery and three infants. Clinical and biochemical data were obtained from probands' medical charts. Genomic DNA was isolated from peripheral blood and CYP24A1 was sequenced. RESULTS: Typical symptoms of hypercalcemia associated with the intake of recommended doses of vitamin D developed in the infants and pregnant woman. Four different loss-of-function CYP24A1 mutations were identified, two of which are reported here for the first time (p.Trp134Gly and p.Glu315*). The infants from families 1 and 2, respectively, were found to be compound heterozygotes, and the infant from family 3 and the pregnant woman were found to be homozygous. CONCLUSIONS: This is the first report of maternal hypercalcemia caused by a CYP24A1 mutation, showing that not only infants are at risk for this complication. Our findings emphasize the importance of recognition, genetic diagnosis and proper treatment of this recently identified hypercalcemic disorder in this era of widespread vitamin D supplements.

Mutations in HAO1 encoding glycolate oxidase cause isolated glycolic aciduria.

BACKGROUND: The primary hyperoxalurias are a group of recessive kidney diseases, characterised by extensive accumulation of calcium oxalate that progressively coalesces into kidney stones. Oxalate overproduction is facilitated by perturbations in the metabolism of glyoxylate, the product of glycolate oxidation, and the immediate precursor of oxalate. Glycolic aciduria associated with hyperoxaluria is regarded as the hallmark of type 1 primary hyperoxaluria. The genetic basis of isolated glycolic aciduria is reported here. METHODS AND RESULTS: Two brothers, born to consanguineous healthy parents of Arab descent, were evaluated for psychomotor delay associated with triple-A-like syndrome (anisocoria, alacrima and achalasia). The proband showed markedly increased urinary glycolic acid excretion with normal excretion of oxalate, citrate and glycerate. Abdominal ultrasound showed normal-sized kidneys with normal echotexture. The genetic nature of triple-A-like syndrome in this kindred was found to be unrelated to this metabolic abnormality. Direct DNA sequencing of glycolate oxidase gene (HAO1) revealed a homozygous c.814-1G>C mutation in the invariant -1 position of intron 5 splice acceptor site. Since HAO1 is a liver-specific enzyme, the effect of this novel mutation on splicing was validated by an in vitro hybrid-minigene approach. We confirmed the appearance of an abnormal splice variant in cells transfected with mutant minigene vector. CONCLUSIONS: Our results pinpoint the expression of defective splice variant of glycolate oxidase as the cause of isolated asymptomatic glycolic aciduria. This observation contributes to the development of novel approaches, namely, substrate reduction, for the treatment of primary hyperoxaluria type I.